Applicants have described methods and apparatus for treating a variety of renal and cardio-renal diseases, such as heart failure, renal disease, renal failure, hypertension, contrast nephropathy, arrhythmia and myocardial infarction, by modulating neural fibers that contribute to renal function, e.g., denervating tissue containing the neural fibers that contribute to renal function. This is expected to reduce renal sympathetic nervous activity, which increases removal of water and sodium from the body, and returns renin secretion to more normal levels. Normalized renin secretion causes blood vessels supplying the kidneys to assume a steady state level of dilation/constriction, which provides adequate renal blood flow. See, for example, Applicants' co-pending U.S. patent application Ser. Nos.: (a) Ser. No. 10/408,665, filed Apr. 8, 2003; (b) Ser. No. 11/129,765, filed on May 13, 2005; (c) Ser. No. 11/189,563, filed on Jul. 25, 2005; (d) Ser. No. 11/363,867, filed on Feb. 27, 2006; (e) Ser. No. 11/504,117, filed on Aug. 14, 2006; as well as U.S. Pat. No. 6,978,174. All of these applications and the patent are incorporated herein by reference in their entireties.
Applicants also have previously described methods and apparatus for intravascularly-induced neuromodulation or denervation of an innervated blood vessel in a patient or any target neural fibers in proximity to a blood vessel, for example, to treat any neurological disorder or other medical condition. Nerves in proximity to a blood vessel may innervate an effector organ or tissue. Intravascularly-induced neuromodulation or denervation may be utilized to treat a host of neurological disorders or other medical conditions, including, but not limited to, the aforementioned conditions including heart failure and hypertension, as well as pain and peripheral arterial occlusive disease (e.g., via pain mitigation). The methods and apparatus may be used to modulate efferent or afferent nerve signals, as well as combinations of efferent and afferent nerve signals. See, for example, Applicants' co-pending U.S. patent application Ser. No. 11/599,649, filed on Nov. 14, 2006, entitled Methods and Apparatus for Intravascularly-Induced Neuromodulation or Denervation, which is incorporated herein by reference in its entirety.
Although the foregoing methods are useful by themselves, one challenge of neuromodulation and/or denervation is sufficiently affecting the neural tissue from within the vessel. For example, intravascular neuromodulation should avoid increasing the risk of acute and/or late stenosis. Therefore, it would be desirable to provide methods and apparatus that further address these challenges.